In order to keep a 3rd-generation mobile communication system competitive in the field of communications, and to provide more personalized mobile communication service with a higher rate and a shorter time delay for a user and lower operation cost of an operator, the 3rd Generation Partnership Project (3GPP) standard working group is dedicated to a research on an Evolved Packet System (EPS). FIG. 1 shows a structure diagram of an EPS, as shown in FIG. 1, the whole EPS includes two parts: a Radio Access Network (RAN) and a core network. The core network includes a Home Subscriber Server (HSS), a Mobility Management Entity (MME), a Serving General Packet Radio Service (GPRS) Support Node (SGSN), a Policy and Charging Rule Function (PCRF), a Serving Gateway (SGW), a Packet Data Network (PDN) Gateway (PGW) and a PDN. Functions of each part will be detailed below:
the HSS includes all functions of a Home Location Register (HLR), is a permanent storage location for subscription data of a user, and is located in a home network subscribed by the user.
The MME is a storage location for the subscription data of the user in a current network, and is responsible for Non-Access Stratum (NAS) signalling management from a terminal to the network, security verification of the terminal, mobility management of the terminal, tracking and paging management in an idle mode of the user and bearer management.
The SGSN is a service support point for the access of Global System for Mobile Communication (GSM) Enhanced Data Rate for GSM Evolution (EDGE) Radio Access Network (GERAN) and Universal Terrestrial Radio Access Network (UTRAN) users to the core network, is functionally similar to the MME, and is responsible for the location updating of the user, paging management, bearer management and the like.
The SGW is a gateway from the core network to a wireless system, and is responsible for user plane bearing from the terminal to the core network, data caching in an idle mode of the terminal, the initiation of a service request by a network side, lawful interception and packet data routing and forwarding; and the SGW is responsible for making statistics on the use of the user terminal over the RAN, generating a ticket for the use of the terminal over the RAN, and sending the ticket to a charging gateway.
The PGW is a gateway of an evolved system and an external PDN of the system, is connected to the Internet and the PDN, and is responsible for the Internet Protocol (IP) address allocation of the terminal, charging, packet filtration, policy control and the like.
A Gateway GPRS Support Node (GGSN) supports an edge routing function of a GPRS network, that is, the GGSN is responsible for performing routing forwarding on the data of the GPRS network, and protecting the integrity of the data of the GPRS network by virtue of a firewall and a filtering function. The GGSN also has a charging function.
The PGW includes all the functions of the GGSN, that is, it can be considered that the GGSN is embedded into the PGW as a sub-function of the PGW. Therefore, the SGSN can be directly connected with the PGW through a Gn/Gp interface.
The PDN is an IP service network of the operator, and provides IP service for the user through the core network of the operator.
The PCRF is a server responsible for providing charging control, online credit control, threshold control and Quality of Service (QoS) policy rules in the evolved system.
The RAN consists of an Evolved Universal Terrestrial Radio Access Network (UTRAN) NodeB (eNB) and a 3G Radio Network Controller (RNC), and is mainly responsible for receiving and sending a radio signal, contacting with the terminal through an air interface and managing a radio resource, resource scheduling and access control of the air interface.
After the six-year development of the EPS since introduction from a 3GPP Release 8 (R8) stage in 2006, new functions are gradually introduced, and almost the function introduction of every time involves the modification of the above functional network elements. Such modification may increase the network upgrading cost of the operator on one hand, and on the other hand, the non-uniformity of degrees of support of different network elements to different functions may also cause a lot of connection test problems because different equipment is provided by different equipment suppliers.